Sounding condenser



Oct. 4, 1932. H. VOGT soUNDING coNDENsER Filed Sept. l5. 1928 2 Sheets-Sheet OOOO OOO OOOOOOO OOOOOOOO Oct. 4, 1932. H. voGT SOUNDING CONDENSER Filed Sept. 15. 1928 2 Sheets-Sheet Pfg. 7.

i Patented Oct. 44,1932

PATENT OFFCE nnisrsvosayor BERLIN-winiviiinsnonr, ern-infirmy souNnING ooivnnnsnn f inventionrelates to sounding condensei'slfor reproduction of speech and music in whic'liaithiul and light diaphragm, is caused torosczillate or vibrate electrostatically, ,and 1 more particularly to animproved condenser of the rstated kind constructed and adapted to reproduce sounds ina most perfectmanner notl realizable in condensers as hitherto constructed. Y i l 19 I' A condenser ,made accordingfto my invenv tioln ishighly sensitive and'adapted to cause ,l thejaltfernating current amplitudes intro- Y duced Qtherein, toproduce or provoke sound ijkpressure fluctuations of great magnitudeas 15 compared withY the sounding condensers as hithertoconstructed, so that all minute inodulations and delicate lvariations of sound and timbre jwilljbe reproduced so as to be clearly distinguishable an'djperceptible to theear.

Another advantage "of my improved conidensers resides in the fact that certain sound Y Vldeformatioi:is or vdistortions which hitherto i could lnot be Vovercome in condensers of this type and which greatly impaired the character-o the reproduction, are minimized 'as vrwillbe Yexplained more indetail hereinafter. i f The quality of reproduced sounds is chiefly impaired in electrostatic devices as hitherto constructed, by the presenceof dispropor- Vtionality between the movement of the `diaphragm and the supplyl of'alternating curvrent' due to the enormous increase'of the intensity of the iield resulting'from the reyduction of the gap'behind or adjacent to the diaphragm.`v Said disproportionality is per- .ceptiblein thefreproduction as aso called non-linear 'or amplitude ldistortionn and produces in vthe reproduction, especially in case of larger amplitudes, additional combination sounds and clattering or jinglingnoises.

Furthermore in all of the electrostatic de,- vices for theA reproduction of sounds ashitherto constructed .and used the low frequencies are reproduced ina faint, poor manner onlydueto 'tlie minimal gap between the diaphragmV and the rigida-structure, resulting "inthe said devices from'the intensive bendling ofthediaphragm', and the consequentlyy reduced movability of the latter'.` It has been suggested to remedy this defect, for instance Yto be able to in myvimproved Y fipplcation'iled September 15, 1928, ySerial No. 306,158, and invGermany May 416, 1928i. i

in the reproductionof speaking lms, by providing particular, onators timed to.

partly encumbering resvarious low frequencies.

advantage requires the provision of quite a multitude of loud-speaking devices in order the low frequencies involves considerabl larly as regards the man voice.

reproduce the whole range of and e disa reproducti just this necessity dvantages particuon of the huen Thechief object of the vpresent invention is to provide a sounding condenser for great performances or etti a novel and advan ciency which constitutes tageous combination of partly known. features with a view to thereby solve and realize the large sound volumes,

problem of producing without possessingthe disadvantages hereinbefore intimated, yrespecting distortion pendence of frequen condenser which is static efficiency and ad sounds in so accurate, manner as never has been attained heretofore.

more than 15V cm'.

speaking, and mount the tween two perforate ble of oscillating free o ly sensitive field bet The electric field Vof of amplitude and decy, and to kthus form a of best l possible electroapted to reproduce clear and natural a employ, accorda diaphragm of size that is of in diameter, generally same midway bed plates so asto be capai" load inthe highween the two plates.

great intensity is produced by a high continuous voltage pressure of ymore than 200 vol rigid structures.

ts to be applied to the The employment of a diaphragm of a large size supported at its circumference only other supporting so as to not have any points and the application of a high electric yfield intensity is lpossible the diaphragm is lo structures so. th

device owing to the fact that cated between two rigid as fregards the high electrostatic forces resulting fromxthe preliminary potential.

.Iyam aware that be electrostatically are in themselves kn diaphragms adapted to l energized on both sides, own in telephones. But v flu Vau

illustrates the oscillating -posi- Vtions of. aV diaphragm of a large diameter at' f' unilateral electrostatic energization; Figure 2 shows two curveswhich illustrate the course forl manner of the oscillations of the dia- -phragm-` depicted in Figure 1; yFigure 3 is a sectional view-similar to Figure 1 at bilateral electrostatic energization; *Figure `4 shows two curves similar to Figure 2, toi illustrate the course'or manner of oscillation of the diaphragmdepicted in Figure 3; Figure 5 is a i .perspective View of a sounding condenser con- 115 structed in'accordance. with the present invention; Figure 6 is a vertical section of the condenser shownin Figure f5, taken on the linefVIY-Vlof Figure 5; Figure 7 is a verktical'section taken on the yline;VII.--V[I of Figure-; Figure 8 is a Vertical section on the line VIII-VIII of'Figure 5; Figure 9 is a sectional view of a spanning and stretching Aframe comprising two annular rings Figfure 10 illustratesnn a sectional View, ythe manzlufactureof the `perforated capacity body of j the condenser inclusive of an auxiliary layer cast integrally therewith; Figure 11 is a fragmentary sectional view of amodilied construction vand formof the two capacity bodies when made of a suitable insulating material;

Figure 12 is adiagram showing the connec- V tions required for operating the sounding l condenser.; FigureV 13 is a front view or elevationjof the condenser accommodated in a ure 14 is a sectional view of the casing shown Y l inl Figure 13. j l, Y

` 1 The Figures 1 .to 4 serve the purpose of showing the diierence between the oscillations of two diaphragms of a large diameter whereof one is arranged so as t0 be unloaded while'the other one is of loaded arrangement,and .which are both lsubjected'to the action of'a strong electric field with an alternating eldsuperposed thereon, in order to illustrate the occurence of-'amplitude distortion in the loadeddiaphragm.

In Figure 1 the svmbol 11 denotesfthe stationary plate and 12 designates the movable diaphragm of ay condenser telephone. The dotted linesshow thediii'erent positions of the diaphragm 12 depending upon the tension. Figure 2 illustrates the conditions by way of two curves, the curve e indicatin the tension and the oscillation of the diaphragm, and the effect of disproportionality hereinbefore mentioned, Vwill be apparen'tfrom Figure 2. The movement of the diaphragm in ydependence upon the alternating lvoltage e is greater at decreasing distance or gap` than at increase of gap.

Thi-Figures e @nativamente the bilateralV l energization of the diaphragms'and further 55 Yshowhow or that unilateral loading of the casing serving as a soundingscreen; and Figdiaphragm is avoided by the two plates 13 and 14 provided on both sides of thelatter so that the ldiaphragm is caused to symmetrically move in both directions; the maximum amplitude S2 in this vcase being substantially greater than s1, that is that of the diaphragm shown in Figure 1.A j

lIn Figures 5 and6 showing a perspective view and across-sectional View of the soundingcondenser, the diaphragm 12 sandwiched betweenV perforated plates 13 and 14.v The diameter of the kefficient portion of the diaphragm may be between 15 and 60 cm., insulatingrings 15 being provided for adjusting the space or gap between the two plates. The peripheral edge of and clamped between two metallic rings 16 yand 17 bymeans of a series of screws 18 symmetricallydisposed in the vtwoV rings. The outer edges ,for faces of the two rings 16 and 17 separately shown in VF igure 9 are enlarged to form inner `annular flanges 19 and 2O adapted to co-operate to grip and hold the peripheral vedge of the diaphragm. Thus it willlbe seen that whenthe screws 18 in the radially projecting ridges are tightened the inner ends of the latter will approach each other as indicated by the arrows 21 in Figure 9 and the two rings will be deformed thereby so that the outer flanges or edges of the rings are displaced in inward direction, indicated by the arrows 22, and the inner flanges 19 and-20 aredisplaced in outward direction as indicated bythe arrows 23 in Figure 9. Consequently the diaphrag 12 peripherally clamped between the two rings 16 and 17 will be spanned and stretched in radial direction when the screws V18 are tightened.

The rings 16 and 17 with the diaphragm 12 under tension constitute a body, as shown inV Figure 9, which'is to be placed between the two'capacity bodies 13 and 14. The latter are shaped to form, when composed as shown in Figure 6, a peripheral annular channel 24 for the reception ofthe rings 16 and 17, aseries of symmetrically arranged spanning screws'25 being provided lin the one or they other. of the two channel-halves, 4so that upon tightening of the screws 25 the interconnected rings 16 and 17 will be displaced laterally and, therefore, the diaphragm will be subjected to a pulling action in radial direction and further stretched gthbttl'l curvem luustratmg the ele y oV 1e cesned degree The dia phragm 12 is not in'touch .with the two lcapacity bodies 13 and 14 since two insulating rings 15V are'provided between the meeting faces of thev capacityv bodies with the diaphragmsupported therebetween. The spanning screws 25 are equipped with resilient washers 26 below the square heads thereof and `adapted to'engage in bushings 27 of insulating material provided in the ring 16, as shown, so that the metallic diaphragm and f7 7 f reame? i the capacity body-13 are not'electrically inter-k l prior to assemblage,l

connected@ j A l Y. y j

The resilient washers, 26 are 'provided for lifthepurposeof exerting a yielding-pullon the screwsf25l and-this pull or draftf'i's transmit- Y ted through the rings 16 .and-17' tothe `dia- Y phragm so /Ivx v l( The. twot capacitybodiesl and .'14 are in- :saine Ymanner asY occur in the diaphragmin the courseof time due toiageing or temperature influences, will at oncebe compensated.V

terconnected by a system jof screws .28 sym'- metrically arranged so that each single screw 28 willbelocated midwaybetween two'fa'dj ar The screwsQS are likewise equipped V.with,resilient 'washers 29 4in vthe described with reference to-y cent screws 25.

the Vscrews 25. The yielding interconnection 'of Vthe two bodies -13 and 14'is necessary or' advisable, order thatv the event of eXpan-v sionY ofthe diaphragm occurring for the above given reasons, the diaphragm will b e allowed to'shiftbetween the twoginsulatingirings15;

The diaphragm 12 is made of'a' very thin and light material-of greattensile strength.

Ipreferablyemploy a material having aten- Y sile strength of 20 to 40 kg. tothe square mm.,

. a specific gravity of-'up Y of-25'to 50 thousandths of a millimetre.

The perforated capacity bodies 18 and 14 consist of a moldable'material and are manufacturedby a casting process with the perforations cast; integrally therewith. j `For the purpose of facilitatingl the casting operation and attaining a uniform casting, VI prefer to cast the capacity bodywith an auxiliary vrlayer SOthereon, see Figurer10,which is subsequently removed by machining, asshown.- Y The material of which'the capacity bodies are made, preferably is a light metal or alloy but it goes without saying that they maybe made justas well of a'moldable 'or'compres-V sibleinsulating 'material such as"bakelite,

porcelain and thelikeand that in sucha case the active-surfacethereof, that is the surface adjacent tothe diaphragm, must be rendered conductive-` v-To this endzthe said surfaceis to be/powderediwith graphite powder andk subsequently galvanically coated with copper. The employment ofcapacity bodies made ofan insulating material as above de scribed is preferable foreconomys sake, they Y arelessl expensive and still canfbe manufac-y turedY with greatl accuracy asVV regards con-V figuration and adjustment. Moreover the insulating rings 151 required Vin case of using vmetallic bodies, v'may' be entirely dispensed with, vif in4 substitution .thereforfthe' inner peripheral edge'of VVthe body V13 and 14 shaped to forni anannular projection or rib 3-1, see Figure 11, vfor ensuringthe gap between the metallic] coatings 32v and 33 of the two v bodies(y fory thediaphragmA 12' toy be vacthecoatingsand 33.1 f

' vcommedated;thereinwithout contacting with thatpany expansions which *mightV "of the rings. `i L to 3 and a thickness` `The 'finished 'capacity bodiesV arecoated, i with an insulating-imm terialpossessing a ,highv dielectricA constant, such as a varnish made,'of'acetylcellulosegor` nitrocellulose.V Also condensation "products of formaldehyde and phenolmay be i emf ployed for that-purpose.- An insulatingnialterial of this ykind invo ,Y tributionlwith ensuring'increase ofthe field intensityin the`Y airgap ybetween the coatings.

In the front of and a distance apart from the' outer. surfaces of the perforated capacity bodies 13' and' 14 there are lirmly'attached to' the' channel-.shaped 'ends thereof protective'sheets- 36jandV 35, respectively, for lthe purpose of,V preventing dust from penetrating through .the 1 perforationsv into the n air: gap'.

The sheets 36 rand 'constitutevery ne thin films preferably made of cellulose' orsiinilar and l prefer to fix tlie'saidsheets matter, Y or films by means of resilient .split rings 37 and SSembedded in `annulared for the purpose' in theY channel-shapedends ofthe bodies -13 V'and 14,"respec'tively,' fandV in which the peripheral edges'of the sheets or films have beenlaid in'prio'rto the insertion V'The efficiency ofy the sounding condenser herein described is largely dependentl onV a ysuitable electric connectionin order that the ylong Wayy ofthe diaphragm available in 'this construction on account of the unloaded Varrangement of the oscillating diaphragm, may be utilized.` AV circuit connection, particularly adapted. for the said purpose is shown in FigureV 12. rlie two" glow Vcathode tubes 42" and `43 arranged in the usual mannerk to operate in lc'ounter-connection',- comprise grids 44 and 45, respectively, to which ajvoltage' in-Y creasedY `in accordancel withV the alternating vvoltage je applied to thefdevice, is suppliedv by means' of lthe translator- 46j, and the vanodes. V40 and 41 of the tubesv42 and 43, respectively,

are interconnected byA a lead 47 including the primary lof a transfor'nier`48'.y The latterfhas a transformation ratio 'of 'l'.to '4and' acts to step up the alteriiating-currents flowing in the lead 47 to avoltagefadapted forthe operation of the loud-speaker. *Theextremities vof the secondary-of the transformer'rl -are lves abetter-4 eld dis-V grooves providy connected with the stationaryvbodies 13 and 14 of the condenser so that the increased al` ternating voltages-willbecome active at the bodies `13 and 14 in opposite'phase and thence will actuate the diaphragmV 12lo'cated thereif between. Tliediaphra'gin 12,*foi'il the one hand, and the two capacity surfaces 13and 14, on the other hand, are loadedlorcharged v to a highpotential constituting a "prel-ii'ninary voltage,"from a voltage source possessing a high internal resistanceor provided,"in'case of Ya lower resistance, withl precursion'oradeinmal high assistances 49 and 5o; g In chargingthe'several-members 12,' 13" vand 14 the one terminal'of,the'vsource of voltage vis 1f" applied to the diaphragm 12 While the other terminal thereof is connected to the circuit 5l acting to interconnect the two stationary' capacity surfaces 13 and 14 through the 5 transformer 48, on the said high preliminary charge or voltage at the differential loudspeaker, there are superimposed the alternating voltages of sound `frequency so as to generate a variable field adapted to vibrate the diaphragm. vThe source of voltage for the` preliminary potential may be a continuous current network. In case of alternating current networks, as in Figure 12, a rectifying device is to be provided, including Va transformer 52 whereof the primary is subjected to the voltv age E of the alternating current network, and the secondary is connected with the cath- 0de of a rectifying tube 55 through a con-V duit 54 and wit-h the anode thereof through a conduit 53, a condenser 56 being included in theconduit 53. The continuous current voltage to be conducted'. through the wires 57 and 58 to the sounding condenser in the man- `ner hereinbefore set forth is gathered from the condenser A56.

The continuous current voltage formed at the condenser 56 may be utilized at the same timetotally or partially 'as anode voltage for operating the tubes 42 and 43, by connecting the wire 57 conducting the positive potential, through the conductors 59 and 60 including choking coils 61 and 62, respectively, for the coupling purpose, with the anodes and 41, respectively, of the tubes 42 and 43 and further connecting the wire 58 conducting the negative potential, through the conduc-j tor 63 with the cathodes 64 and 65 of the tubes 42 and 43.

For purpose of improving the acoustic properties of the sounding condenser I prefer to enclose the sameV in a sounding screen shaped to form a frame or casing 66 made of wood, sheet metal Vorthe like, as shown in VFigures 13 and 14. The yfront wall of the casing consists mainly ofa spherically curved grid 67 covered with a suitable fabric so as tov be pervious to sound, while the rear wall thereof is formed by'aiiat grid 68.- If desired, the casing may be utilized at the same ktime lfor the accommodation of the electrical Vparts or equipment 69 required for the opera- Y tion of the condenser. f

I have hereindescribed and shownonly one practical .construction of my present improvements, but it willbe apparent that the device is susceptible kof embodiment in various other alternative forms, and I, therefore, reserve the privilege of resorting to all such legitimate changes as maybe fairly embodied within the true spirit and scope of the invention as claimed. v Y

What I claim is 1. A sounding condenser consisting `in a diaphragm arranged between twoV perforated rigid electrodes, said diaphragm having a diameter of more thansix inches and consisting of a light metal foil having a thickness of 0.025 to 0.050 mm. of considerable durability of more than 20 kilos per sq. mm., said durability being suitable to sustain a very high radial tension, and the perforated rigid electrodes consisting of an insulating material, the surfaces of the rigid electrodes facing the diaphragm being coated with an electrically conducting layer.

2. A sounding condenser consisting in a diaphragm arranged between two perforated rigid electrodes, said diaphragm having a diameter of more than siX inches and consisting of a light metal foil having athickness Vof 0.025 to 0.050 mm. of considerable durability of more than v20 kilos'per sq. mm., said durability being suitable to sustain a very high radial tension, and the perforated rigid electrodes consisting of an insulating material, the surfaces of the rigid electrodes facing the diaphragm being coated with an electrically conducting layer coated with an insulating lacquer.

3. A sounding condenser consisting of a diaphragm arranged between two perforated rigid electrodes, the diaphragm being peripherally fixed' between two clamping rings with co-operating inner annular anges, and

means including a system of screws provided for interconnecting the two rings 1n such manner that the two co-operating flanges thereof are moved outwards and the diaphragm clamped therebetween is stretched in radial direction.

4. A sounding condenser comprising a dia` phragm arranged between two perforated i rigid electrodes and adapted to communicate on both sides with the air to be agitated, the

diameter of the said diaphragm being greater than six inches, a system of screws for yieldingly interconnecting the two perforated rigid electrodes, and a plurality of spherically bent yielding washers for the screws.

5. A method for producing a perforated 'plate lfor sounding condensers, which comprisesV pressing an insulating material into a plate having a layer on one side and a plurality of depressions extending into the plate on'the other side, and removing the layer from the plate to a thickness or depth to just cut through the depressions whereby the plate will be provided with the perforations.

In testimony whereof I have signed' my name to this specification. l HANS VOGT. 

